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The separation and quantification of underivatized naturally occurring amino acids (AAs) by high-performance liquid chromatography (HPLC) is advantageous for reducing preparation time, running costs, and analytical errors, and is compatible with the isolation of intact AAs. This study establishes and validates an analytical method for the separation and quantification of underivatized AAs and taurine (Tau) in the sub- to several-nanomolar range (ca. 0.1-1.6 nmol) by optimizing ion-pair HPLC coupled to a corona charged aerosol detector (corona CAD). Chromatographic separation of 19 AAs and Tau was achieved using a porous graphite carbon (PGC) column and nonafluoropentanoic acid (NFPA) as a volatile ion-pair reagent. The response of the corona CAD to the AAs was highly dependent on the eluate composition, whereas these response factors were similar for AAs in eluate with similar compositions. Regression curves and coefficients (r 2 ) >0.998 were obtained for plots of injection amount versus peak area, except for Arg which co-eluted with a background peak. On the other hand, all plots of injection amount versus peak height regressed to curves with r 2  > 0.997. Repeat quantification based on peak area showed lower relative standard deviations (RSDs) (typically better than 5%) than those based on peak height. The present method is useful for quantifying AAs from proteins and Tau in the sub- to several-nanomolar range without derivatization, and constant repeatability can be maintained by quantification using peak areas., (Copyright © 2018 Elsevier B.V. All rights reserved.)

We describe the mass descrimination and validation of an offline method for purification of Li, Mg and S with an ion chromatograph coupled to an automated fraction collector for use prior to stable isotope measurements. Significant sub-fraction mass fractionation was observed for both the Li and the Mg stable isotope ratios. The lighter Li and heavier Mg isotopes were preferentially retained by the column, resulting in 7 Li/ 6 Li and 26 Mg/ 24 Mg biases up to 85.8‰ and 0.95‰, respectively. The isotopic compositions of Li, Mg, and S separated from seawater were δ 7 Li L-SVEC  = +30.9‰, δ 26 Mg DSM3  = -0.83 ± 0.10‰, and δ 34 S VCDT  = +19.4 ± 0.6‰; each chromatographic peak was completely recovered, and the results were in good agreement with the published values regardless of whether or not chemical suppressor was used. The purification method enables multi-isotope analysis of a sample using various mass spectrometry techniques, such as multiple-collector inductively coupled plasma and thermal ionization mass spectrometry., (Copyright © 2017 Elsevier B.V. All rights reserved.)

Carbonylation, an oxidative modification of the amino group of arginine and lysine residues caused by reactive oxygen species, has emerged as a new type of oxidative damage. Protein carbonylation has been shown to exert adverse effects on various protein functions. Recently, the role of food components in the attenuation of oxidative stress has been the focus of many studies. Most of these studies focused on the chemical properties of food components. However, it is also important to determine their effects on protein functions via post-translational modifications. In this study, we developed a novel procedure for evaluating the antioxidant capacity of food components. Hydrogen peroxide (H2O2)-induced protein carbonylation in HL-60 cells was quantitatively analyzed by using fluorescent dyes (Cy5-hydrazide dye and IC3-OSu dye), followed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and fluorescence determination. Among a panel of food components tested, quinic acid, kaempferol, saponin, squalene, trigonelline, and mangiferin were shown to be capable of suppressing protein carbonylation in HL-60 cells. Our results demonstrated that this fluorescence labeling/SDS-PAGE procedure allows for the detection of oxidative stress-induced protein carbonylation with high sensitivity and quantitative accuracy. This method should be useful for the screening of new antioxidant food components as well as the analysis of their suppression mechanism., (Copyright © 2016 Elsevier Inc. All rights reserved.)

Pronounced dilation of the maternal vasculature occurs during normal pregnancy. Likewise, low resistance characterizes the fetoplacental circulation. Nitric oxide released by endothelial cells is a potent vasodilator known to be a key modulator of both maternal and fetal vascular tone. However, the mechanisms underlying the maternal circulatory adaptations and the low resistance of the fetal circulation remain unknown. The aim of the present study was to compare levels of asymmetric dimethylarginine (ADMA), an endogenous inhibitor of nitric oxide synthase, in the maternal and fetal circulations. High performance liquid chromatography was used to measure asymmetric ADMA in the maternal and umbilical venous plasma. Plasma ADMA levels during the first trimester were 0.29 +/- 0.05, the third trimester before term 0.29 +/- 0.05, and at term 0.32 +/- 0.05 nmol/mL, which were significantly (P <.05) lower than the levels measured in nonpregnant women (0.41 +/- 0.06 nmol/mL). By contrast, ADMA levels in umbilical venous plasma averaged 1.02 +/- 0.18 nmol/mL, significantly (P <.005) higher than maternal levels. Unlike ADMA, levels of plasma L-arginine, the nitric oxide precursor, did not significantly differ among nonpregnant and pregnant women and the fetus.During pregnancy, maternal hemodynamics are modulated, at least in part, by a reduction in ADMA. Conversely, the low resistance to umbilical blood flow is maintained despite substantially higher fetal ADMA levels. Thus, the predominant mechanisms regulating the maternal and fetal circulation apparently differ.